Production of viscose rayon



Feb. 26, 1952 N, DR|5|| ETAL 2,586,796'

PRODUCTION OF VISCOSE RAYON Filed July 14, 1950 4 Sheets-5h66?. l

Tenna/@ .Y l/ v 2 I .'f I

Feb.' 26', 1952 N DRlsCH Ef AL 2,586,796

PRODUCTION 0F VISCOSE RAYON NICOLAS' DRISCH `ROLAND BlEf-"SQNl l BY , ATTORNEY Feb. 26, 1952 N. bRlscH ET AL PRoDUcTI/ON 0F VISCOSE RAYON 4 Sheets-Shee'il 3 Filed July 14', 1950 INVENTQRS NlcoLAs DRls'cH ROLAND BREPsoN ATTORN F Y Feb. 26, 1952 N DR|$CH ETAL l i l PRODUCTION 0F vIsCosE RAYON Filed July 14, 195o 4 sheets-sheet 4 Patented Feb. 26, 1952 PRODUCTION OF VISCOSE RAYON Nicolas Drsch and Roland Brepson, Paris, France, assignors, by mesne assignments, to Textile and Chemical Research Company Limited, St. Peter, Port of Guernsey, Channel Islands, a corporation of Great Britain Application July 14, 1950, Serial No. 173,924 In Great Britain May 11, 1948 24 Claims. (C1. ,1s- 54) ,This invention relates to the production of viscose .rayon and particularly to the production of viscose rayon of very high quality.

This application is a continuation-in-part Yof co-pendingapplications Serial Nos. 30,153 and 30,154, both filed on May 29, 1948, both now abandoned and includes the subject matter of both of said applications.

`The classical process for the production of viscose rayon consists essentially in .the extrusion (spinning) of a viscose solution through minute oriiices' (a spinnerette) into an aqueous bath (spinning bath) which coagulates and sets the extruded laments. The bath has generally consisted of a dilute solution of sulphuric acid, optionallyv also' containing salts. Considerable research has been directed to the obtaining of laments of high tenacity by this method, and vprocesses have been perfected,` notably those in 'which the laments are stretched continuously with spinning, -whereby products having tenacities as high' as 3.8 to 4.0 gm. per denier have been obtained...

lIn 1926 and subsequent years Lilienfeld proposed a-number of processes based on the use of a spinningbath consisting essentially of a highly concentrated acid, in particular sulphuric acid of 45 to 75% strength by weight. Thus United States Patent No. 1,683,199 describes the use of sulphuric acid of at least 55% strength and United States Patent No. 1,881,740 and Reissue No. 18,170 proposes the substitution of part or all of this acid by another strong mineral acid. In United States Patent No. 1,683,200 Lilienfeld eX- tends the lower limit of the sulphuric acid concentrationfto 45% and uses viscose containing at most5% of caustic alkali. The use of-viscose which is made from alkali cellulose which has been ripened for only a short period is proposed in British Patent No. 317,608 and in this -case it is stated that the sulphuric acid concentration should be not less than 4850% by weight. Final- 1y, ,United States Patent No. 1,881,742 suggests the luse of gaseous mineral acids or. anhydrides as vsetting media.

A survey of Lilienfelds proposals makes it' small extentor to a great extent.

(c) The xanthogenation of the alkali cellulose may be eiected with varying quantities of car- 2 bon disulphide e. g. from 30 to 60% or even as high as 150%, calculated on the weight of the alpha-cellulose in the material treated, (d) The preparation of the viscose may be varied so that the produ-ct contains 5 to 8% or even up to 12% of cellulose and from 8 to 5% or even less of caustic alkali.

(e) The viscose thus prepared may be ripened to a small extent or to a great extent. Y (f) The spinning bath may consist of sulphuric acid of a concentration lying between 45 and by Weight and may contain added salts, and the bath may be used at any temperature between 10 C. and +50 C.

(g) The length of the path of travel of the `laments through the spinning bath may vary from 3 to 200 cm.

(h) The filaments maybe allowed to travel in air after leaving the spinning bath and before they are washed and the length of the path of this travel through the air may be from 20 to 120 cm. or even as great as 200 cm. l

(i) The linear speed of travel of the filaments through the bath may vary from l0 to 60 metres per minute.

(1i) The filaments may be rapidly washed.

(k) The filaments may be stretched by passing over xed bearing surfaces or between rollers rotating at successively increasing speeds.

It is suggested that by the foregoing methods laments can be obtained having a tenacity greater than 2 gm. per denier. i

Though a good real of research has been directed to a study of this process, no really satisfactory technique has hitherto been worked out. By appropriate choice of Working conditions it has been found possible to produce yarns having a tenacity as high as 3 or even 4 gm. per denier but these products lacked sufficient extensibility and were accordingly of little Value for textile purposes, The products also had little resistance to rupture on repeated flexing and were diflicult to dye evenly. The high tenacity of the products suggested that they might have a value in the production of cords for reinforcing pneumatic tyres but the low extensibility of the products rendered them useless for this purpose.

Flor these reasons only a very small quantity of yarn has been produced commercially making use of the Lilienfeld technique. Prior to 1939 such yarn was used for handkerchiefs" and as sewing-yarn; shirts made of it were found to have little resistance to rubbing and soon'frayed at the cuffs.

Attempts were made in Germany during the Society of Dyers and Colourists, volume 61, No.

5. pages 113-118. A feature of this product is the possibility of producing very fine denier yarns, for instance as low as 0.3'denier.

In the following Table I the properties of yarn produced in Germany by the Lilienfeld process and of Durafil yarn are compared:

TABLE I Filament denier Teuacity (dry) gru/denier Tenacity (wet) gm./dc1ner Extension till break (dry) per cent Extension till break (wet) do Knot tenacity (dry) gm./dcn1er Knot `extension till break (dry) per cent Work of rupture The characteristic defined as work of rupture is a measure of the area enclosed between the stress-strain curve or the tenacity-elongation curve and the rectangular axes on which thecurve is plotted.

Rose indicates in the article referred to above, though Durafil can be dyed its dyeing is a lcostly operation and only in some cases can heavy shades be obtained. It is also indicated that-the product is not suitable for the reinforcement of tyres and this is due to the fact that Durafil loses a great deal of its strength when cord-twisted and the cords obtained have a poor resistance to repeated flexing and are, indeed, not as strong as those obtained from normal high tenacity yarn.

From this survey of the prior vart it will be apparent that although the Lilienfeld process shewed considerable promise it has not been possible so far. to produce by means of it yarns of high tenacity and simultaneously of `good extensibility. The present invention is based on the discovery that by a combination of a number of definite conditions it is possible to obtain products of very high quality indeed.

According to the present invention there is pro-- vided a process for the production of high quality viscose rayon filaments having in the Aair-dry condition a tenacity greater than 4.8 gm. per denier and an elongation at the breaking point greater than 8%, which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cellulose containing less than by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecu- Alar chains with a degree of polymerisation below 250, said viscose being prepared via alkali-cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose 4has a degreeof Xanthogenation (y) (as hereinafter defined) between and 50, the concentration of sulphuric acid in the said bath being defined by the formula:

'Percentage concentration by weight of sulphuric acid:1.26y|8i3 thereafter subjecting the extruded vfilaments to., 'I5

4 a stretching operation to increase their length by to 280% while they are still wet from the spinning bath, washing the filaments and allowing them to relax, and then winding or winding and twisting the filaments thusobtained.

Further, in a preferred form of this invention there is provided a process for the production of ,high quality viscose rayon filaments having in the air-dry condition a tenacity greater than 5.0 gm. per denier and lan elongation at the breaking point greater than 8.5% which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cellulose Acontaining yless than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular vchains with'a degree of polymerisation below 250, said viscose being prepared via alkali cellulose-of which the mean degree of polymerisation after ripening is greater than 450, which viscose has a degree 'of xanthogenation (y) (as hereinafter defined) between 4.4.and 47, the concentration of sulphuric acid in the said .bath being -defined by the formula:

'Percentage concentration by weight of sulphuric acid:"1.'26y+8i2 thereafter subjecting the extruded :filaments to a stretching operation to Yincrease rtheir length by 20G-250% while they are .still wet vfrom Vthe spinning bath, washing the filaments and allowing them to relax, and then winding or winding and ytwisting the filaments thus obtained.

The degree of polymerisation, by Aweight average, is determined bymeasuring the'viscosity of a carefully prepared cellulose nitrate in'anappropriate organic solvent and multiplying the viscosity thus determined by the'constant defined by Staudinger. The solution of cellulose jor of the corresponding cellulose nitrate .may be :fractionated and the mean chain .length lor degree of polymerization of the Afractions determined :in the same way (see H. Dostal and H. Mark, Transactions of the Faraday Society, volume .33, 1937, and N. Drisch, Etudes de la Cellulose, Conference de Perfectionnement Technique, Maison de la Chemie, Paris). The composition of some typical pulps is set out in Table II.

From the foregoing Table II it will be seen that purified cotton linters are very suitable as a raw material for the production of viscose for use in this invention but the typical wood pulps are not. Nevertheless it should be understood -that the present invention is not restricted to the use of cotton linters and that a wood pulp meeting the requirements of degree of polymerisation of the cellulose, as set out above, may also'be employed. Celluloses of relatively short vchain length yield viscose filaments more readily soluble in strong sulphuric acid and for that reason `are unsuitable starting materials.

The degree of Xanthogenation of the cellulose, represented by the symbol y, is the number of hydroxyl groups substituted by -CSS- groupsv per 100 glucose units (i. e. CeHioOs units)l 'y-Values below 40 are impracticable since they yield products of low extensibility and an upper limit is set by the fact that sulphuric acid of strength much greater than 72% has so strong aA dissolving action on the viscose laments that very rapid washing indeed becomes necessary.

In the preparation of the viscose from the cellulose via alkali-cellulose it is preferred to adjust the conditions so as to obtain a viscose containing not more than '7% of cellulose and not less than 6.5% of caustic soda lye (preferably between 6.5 and 8.2% of caustic soda lye). The viscosity of the viscose should be greater than 150 C. G. S. units and preferably greater than 200-250 C. G. S. units.

In the accompanying drawings:

Figure l is a three dimensional diagram showing the optimum tenacities obtained from the best combination of concentrations of acid and y values.

Figure 2 is a graph showing the tenacities obtained from combinations of concentrations of acid and specific y values.

Figure 3 is a graph comparing the extensibility and tenacity of various type yarns. l

Figure 4 is a photomicrograph of a cross-section of the Lilienfeld yarn.

Figure 5 is a photomicrograph of a cross-section of the yarn of this invention.

In a three-dimensional diagram with the 'y'- value on the X-axis, percentage concentration of acid on the Y-axis and tenacity or elongationI on the Z-axis, the expression C'zfw) is substantially a straight line in the XY plane. A vertical plane through this line contains a curve representing the optimum tenacities (or elongation) for the best combination of concentration and y. The form of the three dimensional diagram is illustrated in Figure 1 of the accompanying drawings.

The highest quality products are obtained using viscose of y-value about 45 and an acid concentration about 65%.

The optimum acid concentration for a viscose of particular 'y-value is determined by the formulae set out above and represents the apex of the curve, of somewhat paraboloidal shape, which, for a given 'y-value, connects the tenacity with the sulphuric acid concentration. The variation i3% included in the rst formula above affords a margin on either side of the optimum value at which products having prop*- erties close to the optimum are obtained, and the variation f-2 affords a narrower margin within which the preferred products are obtained. Curves connecting tenacity (wet and dry) with acid concentration for the limiting 'y-values of 40 and 50, and for their intermediate values in accordance with this invention, are illustrated in Figure 2.

As already stated, the filaments should be stretched to the extent of 150-280% and preferably 200-250% continuously with their production and while they are still wet from 'the spinning bath. (The degree of stretch is calculated as the ratio of the increase in length to the original length.) In this connection it is preferable to employ the process described in copending application No. 9,915, led February 19, 1948, now Patent No. 2,538,151 wherein the coagulated filaments are stretched and then led over at least one feed roller before passing to a winding device, the thread being caused to travel 3, 5 or 10 or more metres under tension in air between the feed roller and the winding device for a period of at least three seconds. By this means the tension in the yarn is allowed to even out and a more homogeneous yarn, with less internal strains, is obtained. By allowing the yarn to relax, by removing the stretching tension, a product is obtained which has less tendency to shrink than the usual stretched yarn.

The following specic examples will serve to illustrate the invention but are not to be regarded as limiting the invention in any way.

Example I For the preparation of the viscose, carefully bleached cotton linters having the following properties was selected:

Alpha-cellulose content per cent-- 98.2 Solubility in 7 caustic soda lye at 90 C.

l per cent 1.8 Mean degree of polymerisation 850 Chains with degree of polymerisation above 500 per cent-- 75.2 Chains with degree of polymerisation between 250 and 500 per cent 22.0 Chains with degree of polymerlsation below 250 per cent 2.8

The weight average distribution of the chain lengths of the cellulose molecules was determined, by the method described above, using a arefully prepared nitrocellulose dissolved in aceone.

100 kg. of these cotton linters in sheet form were immersed in a bath containing 220 gm. of caustic soda per litre at 21 C. The sheets were then pressed so that 300 kg. of alkali-cellulose were obtained. The alkali-cellulose was then shredded over a period of three hours at 18 C. and during this operation 500 gm. of pine oil was added. The resulting iiuffy mass was ripened for 6 hours at 18 C. The mean chain length of the alkali-cellulose at this stage corresponded to a degree of polymerisation of 500.

l a viscose solution containing 6.3% cellulose and 7.8% caustic soda. During the dissolution the temperature, at first reduced to 6 C. rose over 5 hours to 14 C. Towards the end of the dissolution period 1 kg. of a scum-preventing material (e. g. a mixture of the higher branched aliphatic alcohols) was added. The viscose was then degassed over a period of 8 hours at a vacuum of 750 mm. of mercury. The viscosity of the product was then 205 C. G. S. units and the viscose, after maturing for 40 hours at 14 C. was found to have a 'y-value of 43.5.

vThe viscose thus obtained was spun through a spinnerette of 800 holes, each 0.06 mm. diameter, into a bath containing 62.8% by weight of sulphuric acid, at 18 C. The extruded filaments travelled through the bath a distance of 45 cm. and were then passed. round a rst roller 10 cm. diameter rotating at 64 R. P. M. and then round a second roller of the same size rotating at 200 R. P. M.

The stretched yarn was then passedv into. an

aqueous washing bath iat 20910. having the -fol lowing composition:

(such a bath may be a used spinning bath).

The yarn travelled for 100 cm. in this bath and was then passed on to a third roller, similar to the rst and second rollers but rotating at only 195 R. P. M. By this means the yarn was allowed to relax. Finally the yarn was wound up in a conventional spinning pot rotating at '7500 R. P. M. The volume of viscose fed to the spinnerette was controlled by a pump so that a 300 denier yarn was obtained.

The yarn was then completely de-acidied with water and then treated with a 1% solution of sulphonated cetyl alcohol. It then had the For the preparation of the viscose, carefullyv bleached cotton linters having the following properties were selected:

4Alpha-cellulose content 'per cent 98.2 Solubility in '7% caustic soda lye at 90 C.

per cent 1.8 Mean degree of polymerisation 1250 Chains with degree of polymerisation above 500 -per cent 83.8 Chains with degree of polymerisation between 250 and 500 per cent 15.0 Chains with degree of polymerisation below 250 per cent v 1.2

The weight average distribution of the chain lengths of cellulose molecules was determined, by the method described above, using a carefully prepared nitrocellulose dissolved in acetone.

100 kg. of these cotton linter's in sheet form were immersed in a bath contain 220 gm. of

caustic soda per litre at 21 C. The sheets were y then pressed so that 300 kg. of alkali-cellulose were obtained. The alkali-cellulose was then shredded over a period of three hours at 18 C.

and during this operation 500 gin. of pine oil wasadded. The resulting fluify mass was ripened for` l2hours at 17 C. The mean chain length of the alkali-cellulose at this stage corresponded 'toa degree of polymerisation of `500.

The alkali-cellulose was then placed in a churn of known type and a vacuum of 720 mm.' ofmerfcury was applied. 45 kg. of carbon disulphide was then added and the churn slowly rotated for two vhours at 25 C.

The cellulose xanthate thus obtained was dissolved in cold dilute caustic soda'lye to produce a viscose solution containing 5.9% cellulose and '8.0% caustic soda. During the dissolution the temperature, at rs't reduced to 6C.' rose-over f5 yhours to 14' C. Towards the end of the dissolution'lperio'd 1 kg. of a scum-preventing material '(e. g. a mixture of the higher branched ali- .zphatic alcohols) Ywas added. The viscose was :then degassed over a period of 8 hours'at avacuum of r150 mm. of mercury. The `viscosity of the iproduct wasthen 280C. G..S. units and. the viscose. 'after maturing ,for 36" hours at 14 C was found 'to have a y-value of 46.

The viscose thus obtained was spun through .a spinnerette of 600 holes, each 0.06 mm. diameter, into a bath containing 66% by weight of sulphuric acid, at 18 C. The extruded filaments travelled through the bath a distance of 50 cm. and were then passed round two rollers in suc'- cession, each of 10 cm. diameter but rotating at different speeds so as to stretch the filaments to the extent of 240%. The filaments lapped round the second of these rollers 10 turns and the roller was combined with an off-set rod so as to cause automatic displacement of the turns.

The stretched yarn was then passed into an aqueous washing bath at 20 C. having the following composition:

Gm./1itre Sodium sulphate 200 Sulphuric acid 140 (such a bath may be a used spinning bath).

The yarn travelled for cm. in this bath and was then passed on to a third roller, similar to the first and second rollers but rotating at a slightly lower speed than the second roller. By this means the yarn was allowed to relax. Finally the yarn was wound up in a conventional spinning pot rotating at 7500 R. P. M. The volume of viscose fed to the spinnerette was controlled by a pump so that a 300 denier yarn was obtained.

The yarn was then completely de-acidied with water and then treated with a 1% solution of sulphonated cetyl alcohol. It then had the following properties:

Tenacity (dry) gm/denier.. .5.7 Tenacity (wet) do 4.6 Elongation (dry) p,er cent-- v9.5 Elongation (wet) do 10.0 Work till rupture gm. cm./metre/denier 23.2 Mean degree of polymerisation 560 Loop tenacity gm/denier-.. 4.0 Loop elongation per cent 6.8

The products obtained by the process of the present invention therefore present important advantages over the products hitherto produced. Thus the yarns of this invention have a higher extensibility (elongation at break) for the same or higher tenacity and have a higher relative value of wet to dry tenacity. They have a higher work-till-rupture value and this is illustrated in Figure 3 of the accompanying drawings in which the curves for the products Tenasco and Dural, calculated from the data given by L. Rose in the paper referred to above, are compared with a product of the foregoing Example II identiiied as curve P. The values for work-till-rupture for Tenasco and Durail are 24.2 and 14.3 respectively, and the value for the yarn P is 23.2 calculated on the same basis. The yarns of this invention have good flexibility and knot strength and the facility with which they may be twisted and woven renders them suitable for ordinary textile uses as well as for cord-twisting for the reinforcement of tyres, for which latter purpose their high degree of elongation at break (greater than 8%) makes them particularly suitable.

While yarns previously prepared by the Lilienfeld process have shewn cracks and splits, especially visible in transverse sections, yarns produced in accordance with the present invention have far fewer and less extensive cracks and splits.A y

This lslllustrated in Figures 4 and 5 of the accompanying drawings which are photomicrographs of cross sections of the Lilienfeld yarn (Figure 4) and of the yarn in accordance with the present invention (Figure 5).

Moreover, it is to be noted that yarns produced in accordance with the present invention dye readily and evenly, comparing favourably with comercial high tenacity viscose yarns.

We claim:

1. Process for the production of high quality viscose rayon laments having in the air-dry condition a tenacity greater than 4.8 g. per denier and an elongation at the breaking point greater than 8% which process comprises extruding into a bath of sulphuric acid at normal room temperature aviscose prepared from cellulose containing less than by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular chains with a degree of polymerisation below 250, said viscose being preparedQvia alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose has a degree of xanthogenationiv) between and 50, the concentration of sulphuric acid in the said bath being defined by the formula:

Percentage concentration by weight of Y sulphuric acid=l.26y+8:n3

thereafter subjecting the extruded filaments to a stretching operation to increase their length by 150-280% while they are still wet from the spinning bath, washing the filaments in a more dilute acid bath and allowing them to relax while still in the acid condition and winding or winding and twisting the filaments thus obtained.

2. Process for the production of high quality viscose rayon filaments having in the air-dry condition a tenacity greater than 4.8 g. per denier and an elongation at the breaking point greater than 8% which process comprises extruding into a bath of/sulphuric acid at normal room temperature a viscose prepared from cotton linters containing less than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular chains Witha degree of polymerisation below 2.50, said viscose being prepared via alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose has a degree of xanthogenation ('y) between 40 and 50, the concentration of sulphuric acid in the said bath being defined by the formula:

Percentage concentration by weight of 1 sulphuric acid=1.26'y+8i3 thereafter subjecting the extruded filaments to a stretching operation to increase their length by 150-280% while they are still wet from the spinningbath, washing the filaments in a more dilute acid' bath and allowing them to relax while still in thelacid condition and then winding or winding and y.tv'visting the filaments thus obtained.

33;.Process for the production of high quality visco'selrayon laments having in the air-dry con; ditiona tenacity greater than 4.8 g. per denier and an elongation at the breaking point greater than 3% which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cellulose containing less than 25% by weight vof molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared via 'alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose has a degree of xanthogenation ('y) between 40 and 50, the said viscose containing at most '7 of cellulose and at least 6.5% of caustic soda lye, the concentration of sulphuric acid in the said bath being defined by the formula:

Percentage concentration by weight of sulphuric acid=1.26fy+8 *3 thereafter subjecting the extruded filaments to a stretching operation to increase their length by -,280% while they are still wet from the spinning bath, washing the filaments in a more dilute acid bath and allowing them to relax while still in the acid condition and then winding or winding and twisting the filaments thus obtained| 4. Process for the production of high quality viscose rayon filaments having in the air-dry condition a tenacity greater than 4.8 g. per denier and an elongation at the breaking point greater than 8% which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cellulose containing less than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose has a degree of xanthogenation (y) -between 40 and 50, the said viscose containing at most 7% of cellulose and at least 6.5% of caustic soda lye and having a viscosity greater than 150 C. G. S. units, the concentration of sulphuric acid in the said bath being defined by the formula:

Percentage concentration by weight of sulphuric acid=1.26-y+8i3 4a bath of sulphuric acid at normal room temperature a viscose prepared from cellulose containing less than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 5% by weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared va alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose has a degree of xanthogenation (y) between 40 and 50, the said viscose containing at most '7% of cellulose and at least 6.5% of caustic soda lye and having a viscosity greater than 250 C. G. S. units, the concentration of sulphuric acid in the said bath being defined by the formula:

Percentage concentration by weight ci sulphuric acid=1.26y+8 f3 thereafter subjecting the extruded filaments to a stretching operation to increase their length by 150-280% while they are still wet from the spinning bath, washing the filaments in a more dilute acid bath and allowing them to relax while still in the acid condition and then winding or Winding and twisting the laments thus obtained.

6. Process for the production of high quality viscose rayon iilaments having in the air-dry condition a tenacity greater than 4.8 g. per denier and an elongation at the breaking point greater than 8% which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cotton linters containing less than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which Viscose has a degree of xanthogenation ('y) between 40 and 50, the said Viscose containing at most '7% of cellulose and at least 6.5% of caustic soda lye, the concentration of sulphuric acid in the said bath being defined by the formula:

Percentage concentration by weight of sulphuric acid=1.26^/!8i3 thereafter subjecting the extruded filaments to a stretching operation to increase their length by G-280% while they are still wet from the spinning bath, washing the ilaments in a more dilute acid bath and allowing them to relax while still in the acid condition and then winding or Winding and twisting the filaments thus obtained.

'7. Process for the production of high quality viscose rayon laments having in the air-dry condition a tenacity greater than 4.8 g. per denier and an elongation at the breaking point greater than 8% which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cotton linters containing less than by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose has a degree of xanthogenation (v) between 40 and 50, the said'viscose containing at most 7% of cellulose and at least 6.5% of caustic soda lye and having a viscosity greater than 250 C. G. S. units, the concentration of sulphuric acid in the said bath being defined by the formula:

Percentage concentration by weight of sulphuric acid=l.26^y+8i3 thereafter subjecting the extruded filaments to a stretching operation to increase their length by 15G-280% while they are still wet from the spinning bath, washing the filaments in a more dilute acid bath and allowing them to relax while still in the acid condition and then winding or winding and twisting the filaments thus obtained.

8. Process for the production of high quality viscose rayon filaments having in the air-dry 12 polymerisation after ripening is greater than 450. which viscose has a degree of xanthogena tion (y) between 40 andV 50, the concentration of sulphuric acid in the said bath being dened by the formula:

Percentage concentration by weight .l

of sulphuric acid=1.26y+84 '3 thereafter subjecting the extruded filaments td a stretching operation to increase their length by 280% while they are still wet from the spinning bath. washing the filaments in a more dilute acid bath and then causing them to travel in free air under insuicient tension to cause stretching for a distance of at least three metres and for a period of at least three seconds, thus allowing the filaments to relax while still in the acid condition and then winding or winding and twisting the laments thus ob tained.

9. Process for the production of high qualityv viscose rayon filaments having in the air-dry condition a tenacity greater than 4.8 g. per denier and an elongation at the breaking point greater than 8% which process comprises ex# truding into a bath of sulphuric acid at normal room temperature a viscose prepared from cotton linterscontaining less than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose has a degree of xanthogenation (y) between 40 and 50, the concentration of sulphuric acid in the said bath being deiined by theformula:

Percentage concentration by' weight of sulphuric acid=1.26fy|8i3 thereafter subjecting the extruded laments to a stretching operation to increase their length by 15G-280% while they are still wet from the spinning bath. washing the laments in a more dilute acid bath and then causing'them to travel in free air under insuincient tension to cause stretching, for a distance of at least three metres and for a period of at least three seconds;

` thus'allowing the iilaments to relax While-still in the acid condition and then winding or wind-f ing and twisting the filaments thus obtained. 4

10. Process for the production of high quality viscose rayon laments having in the air-dry condition a tenacity greater than 4.8 g. per denier and an elongation at the breaking point greater than 8% which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cot ton linters containing less than 25% by weight of molecular chains with a degree of polymer-L isation below 500 and less than 4% by weight of molecular chains with a degree'of polymer isation below 250, said viscose being' prepared via alkali cellulose of which the mean degree of polymerisation after ripening greater than 450, which viscose has a degree-of xanthogenafE tion (v) between 40 and 50, the said viscose containing at most 7% of cellulose and'at'v least 6.5% of caustic soda lye,r the concentration of sulphuric acid in the saidbath being defined'b'y the formula: f Percentage concentration by weightv .f of.` sulphuricL-.acid=.`1.26'y1l:8:3

thereafter subjecting the extruded laments to a stretching operation to increase their length by 15G-280% while they are still wet from the spinning bath, washing the filaments in a more dilute acid bath and then causing them to travel in free air under insufficient tension to cause stretching, for a distance of at least three metres and for a period of at least three seconds, thus allowing the iilaments to relax while still in the acid condition and then winding or winding and twisting the filaments thus obtained.

11. Process for the production of high quality viscose rayon filaments, having in the air-dry condition a tenacity greater than 4.8 g. per denier and an elongation at the breaking point greater than 8% which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cotton linters containing less than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose has a degree of xanthogenation ('y) bewteen 40 and 50, the said viscose containing at most 7% of cellulose and atleast 6.5% of caustic soda lye and having a viscosity greater than 250 C. G. S. units, the concentration of sulphuric acid in the said bath being dened by the formula:

Percentage concentration by weight of sulphuric acid=1.26y+8i3 thereafter subjecting the extruded filaments to a stretching operation to increase their length by 15G-280% while they are still wet from the spinning bath, washing the filaments in a more dilute acid bath and then causing -them to travel in free air under insuflicient tension to cause stretching, for a distance of at least three metres and for a period of at least three seconds, thus allowing the laments to relax while still in the acid condition and then winding or winding and twisting the filaments thus obtained. Y

12. Process for the production of high quality viscose rayon laments having in the air-dry condition a tenacity greater than 5.0 g. per, denier and an elongation at the breaking point greater than 8.5% which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cellulose containing less than 25% by weight of molecular chains with a degree f polymerisation below 500 and less than 4% by weight of molecular ychains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose has a degree of xanthogenation (y) between 44 and 47, the concentration of sulphuric acid in the said bath being defined by the formula:

Percentage concentration by weight of sulphuric acid=1.26y|-8 l2 thereafter subjecting the extruded filaments to a stretching operation to increase their length by 20G-250% while they are still wetfrom' the spinning bath, washing the filaments in a more dilute 'acid bath and allowing them to relax whilestill in the acid condition and then wind- 14 ing or winding and twisting the laments thus obtained.

13. Process for the production of high quality viscose rayon filaments having in the air-dry condition a tenacity greater than 5.0 g. per denier and an elongation at the breaking point greater than 8.5% which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cotton linters containing less than 2,5% by weight of molecular chains, with a degree of polymerisation below 500 and less-than.4% by weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose lhas a Percentage concentration by weight thereafter subjecting the extruded filaments to a stretching operation to increase their length by 20D-250% while they are still wet from the spinning bath, washing the filaments in a more dilute acid bath and allowing them to relax while still in the acid condition and then winding or winding and Vtwisting the filaments thus obtained.-

14. Process for .the production of high quality viscose rayon filaments having in the air-dry con-` dition a tenacity greater than 5.0 g. per denier and an elongation at the breaking point greater than 8.5% which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cellulose containingless. than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose has a degree of xanthogenation (y) between 44 and 47, the said viscose containing at most 7 of cellulose and at least 6.5% of caustic soda lye, the concentration of sulphuric acid in the defined by the formula:

Percentage concentration by weight of sulphuric acid=1.26"y}-8i2 said bath being thereafter subjecting the extruded filaments to a stretching operation to increase their length by 20o-250% while they are still wet from the spinning bath, washing the laments in a more dilute acid bath and allowing them to relax while still inthe acid condition and then winding or winding and twisting the filaments thus obtained.

15. Process for the production of high quality viscose rayon laments having in the air-dry condition a tenacity greater than 5.0 g. per denier and an elongation at the breaking point greater than 8.5% which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cellulose containing less than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean degree of polymerisation after ripening-is greaterthan- 450,"which viscose has a degree of xanthogenation (y) between 44 and 47, the-said viscose containing at most 7% of cellulose and at least 6.5%` of caustic soda lye and having a l viscosity'greater than 150y C. G; S. units,'the concentration of sulphuric acid in the said. bath. being defined by the formula:

Percentage concentration by weight of sulphuric acid=1.26^y`+8i2 thereafter subjecting the extruded iilamentsr to a stretching operation to increase their length. by 20G-250% while they are still wetl from the spinning bath, washing the filaments in a more dilute acid' bath and allowing them to relax while still in the acid condition and then winding or winding and twisting the filaments thus obtained.

16. Process for the production of high quality viscose rayon filaments having in the air-dry condition a tenacity greater than 5.0 g. per denierand anelongation at the breaking point greater than 8.5% which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cellulose containing less than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight oimolecular chains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose has a degree of xanthogenation ('y) between 44 and 47, the said viscose containing at most 7% of cellulosefand at least 6.5% of caustic soda lye and havinga viscosity greater than-250 C. G. S. units. the concentration of sulphuric acid in the said bath being deiined by the formula:

Percentage concentration by weight of sulphuric acid=1.26'y+8i2 thereafter subjecting the extruded filaments to a stretching operation to increase their length by 20G-250% while they are still wet from the spinning bath, washing the laments in a more dilute acid bath and allowing them to relax while still in the acid condition and then winding or winding and twisting the laments thus obtained.

17. Process for the production of high quality viscosev rayon filaments having in the air-dry condition a tenacity greater than 5.0 g. per denier` and an. elongation at the breaking pointv greater than 8.5% which process comprises extruding into a bath of sulphuric acid at normal room temi perature a viscose prepared from cotton linters l containingless than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean degree of polymerisationV afterj ripening is greater than 450, whichviscose has a' degree of xanthogenation (y) between 44 and 47, the said viscose containing at most 7% of cellulose and at least 6.5% of caustic soda lye, they concentration of sulphuric acid in the said bath being dened by the formula:

Percentage concentration by weight l of sulphuric acid=l.26y+8 L-2 and' an elongation at the breaking' point great'- er than 8.5% which process comprises extruding into a bath of sulphuric acidv at normal room temperature a viscose prepared from cotton linters containing less than 25% by weight of molecular chains with a degree of polymerisationv below 500 and less than 4% by weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean. degree of polymerisation.- after ripening is greater than 450, which viscose has a degree of xanthogenation (fy) between 44 andv 47, the said viscose containing at most 7% of cellulose and at least 6.5 of caustic soda lye and having a viscosity greater than 250 C. G. S. units, the. concentration of sulphuric acid in the said bath being dened by the formula:

Percentage concentration by weight of sulphuric acid=l.26fy+8- I2 thereafter subjecting the extruded iilaments to a stretching operation to increase their length by 20G-250% while they are still wet from the spinning bath, washing the filaments in a more dilute acid bath and allowing them to relax while still in the acid condition and then winding or winding and twisting the filaments thus obtained.

19. Process for the production of high quality viscose rayon iilaments having in the air-dry condition a tenacity greater than 5.0 g. per denier and an elongation at the breaking point greaterI than 8.5% which process comprises extruding into a bath of sulphuric acid at normal room ternperature a viscose prepared from cellulose containing less than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose has a degree of xanthogenation (y) between 44 and 47 the concentration of sulphuric acid in the said bath being defined by the formula:

Percentage concentration by weight of sulphuric acid=l.26y{8i2 thereafter subjecting the extruded filaments to a stretching operation to increase their length by 20G-250% while they -are still wet from the spinning bath, washing the filaments in a more dilute acid bath and then causing them to travel in free air under insufficient tension to cause stretching, for a distance of at least three metres and for a period of at least three seconds, thus allowing the laments to relax while still in the acid condition and then winding or winding and twisting the filaments thus obtained.

20. Process for the production of high quality viscose rayon filaments having in the air-dry condition a tenacity greater than 5.0 g. per denier and an elongation at the breaking point greater than 8.5% which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cotton linters containing less than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular chains with a degree oi polymerisation below 250, said viscose being prepared via alkali cellulose4 of which the mean degree of polymerisation afterv ripeningis greater than 450, which viscose has a degree of xanthogenation ('y) between 44 and 47,

the concentration of sulphuric acid in the said bath being dened by the formula:

Percentage concentration by weight of sulphuric acid=l.26fyI-8;L2

thereafter subjecting the extruded filaments to a stretching operation to increase their length by 20G-250% while they are still wet from the spinning bath, washing the laments in a more dilute acid bath and then causing them to travel in free air under insufficient tension to cause stretching, for a distance of at least three metres and for a period of at least three seconds, thus allowing the filaments to relax while still in the acid condition and then winding or winding and twisting the filaments thus obtained.

21. Process for the production of high quality viscose rayon filaments having in the air-dry condition a tenacity greater than 5.0 g. per denier and an elongation at the breaking point greater than 8.5 which process comprises extruding into a bath of sulphurc acid at normal room temperature a viscose prepared from cotton linters containing less than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by Weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean degree of polymerisation after ripening is greater than 450, which viscose has a degree of xanthogenation (y) between 44 and 47, the said viscose containing at most '7% of cellulose and at least 6.5% caustic soda lye, the concentration of sulphuric acid in the said bath being dei-ined by the formula:

Percentage concentration by Weight of sulphuric acid=1.26y+8i2 thereafter subjecting the extruded laments to a Stretching operation to increase their length by 20G-250% while they are still wet from the spinning bath, washing the filaments in a more dilute acid bath and then causing them to travel in free air under insufficient tension to cause stretching, for a distance of at least three metres and for a period of at least three seconds, thus allowing the laments to relax while still in the acid condition and then winding or winding and twisting the laments thus obtained.

22. Process for the production of high quality viscose rayon filaments having in the air-dry condition a tenacity greater than 5.0 g. per denier and an elongation at the breaking point greater than 8.5 which process comprises extruding into a bath of sulphuric acid at normal room temperature a viscose prepared from cotton linters containing less than 25% by weight of molecular chains with a degree of polymerisation below 500 and less than 4% by weight of molecular chains with a degree of polymerisation below 250, said viscose being prepared via alkali cellulose of which the mean degree of `polymerisation after ripening is greater than 450, which viscose has a degree of xanthogenation (7) between 44 and 47, the said viscose containing at most 7% of cellulose and at least 6.5% of caustic soda lye and having a viscosity greater than 250 C. G. S. units, the concentration of sulphuric acid in the said bath being dened by the formula:

Percentage concentration by weight of sulphuric acid: 1.26y 8 i 2 thereafter subjecting the extruded laments to a stretching operation to increase their length by 20G-250% while they are still wet from the spinning bath, washing the laments in a more dilute acid bath and then causing them to travel in free air under insufficient tension to cause stretching, for a distance of at least three metres and for a period of at least three seconds, thus allowing the laments to relax while still in the acid condition and then winding or winding and twisting the filaments thus obtained.

23. Viscose rayon filaments having in the airdry condition a tenacity greater than 4.8 g. per denier and an elongation at breaking point greater than 8% and having a work-till-rupture value greater than 20 g. cm./metre/denier, and made by the process defined in claim 1.

24. Viscose rayon iilaments having in the airdry condition a tenacity greater than 5.0 g. per denier and an elongation at breaking point greater than 8.5% and having a work-till-rupture value greater than 20 g. cm./metre/denier, and made by the process dened in claim 12.

NICOLAS DRISCH. ROLAND BREPSON.

No references cited. 

1. PROCESS FOR THE PRODUCTION OF HIGH QUALITY VISCOSE RAYON FILAMENTS HAVING IN THE AIR-DRY CONDITION A TENANCITY GREATER THAN 4.8 G. PER DENIER AND WHICH COMPRISES PROVIDING A SUPPLY OF WATER, TAKING FLUID PRESSURE FROM A COMBUSTION CHAMBER OF THE ENGINE, AND USING SUCH PRESSURE FOR INJECTING WATER INTO THE FUEL. 